3-D Numerical Simulation of Turbidity Currents in Submarine Canyons off the Niger Delta

Abstract

A three-dimensional unsteady numerical model is applied to simulate turbidity currents in deep submarine canyons located on the continental slope of the Niger Delta. In one of the few attempts to compare field core data to numerical simulations, we conduct several high resolution flow simulations with various boundary conditions to predict the grain size and deposition rates and compare the results to grain size and bed thickness from 22 piston cores collected at different elevations above the canyon thalweg. The model solves the Reynolds-averaged Navier–Stokes equations (RANS), the Mellor–Yamada turbulence closure equations, and the sediment conservation equations for different grain size classes. The bed evolution is modeled using the Exner equation of sediment conservation allowing adjustment of the numerical grid due to bed level changes caused by sediment entrainment/deposition during each time step. The simulated flow fields suggest that turbidity current dynamics is strongly controlled by the seafloor topography. Simulated mean bed thickness and grain size show trends where values of bed thickness and grain size are fining upwards with the elevation above the channel thalweg.